This aerial photo shows a 27-foot boat floating above the edge of a sinkhole in Lake Huron's Thunder Bay.

A team of scientists from Grand Valley State University and the National Oceanic and Atmospheric Administration's Great Lakes laboratory have discovered sinkholes -- similar to deep sea vents in oceans -- on the bottom of Lake Huron's Thunder Bay.

The sinkholes, formed by salty groundwater seeping into the lake and dissolving the ancient underlying seabed, are found offshore of Alpena in about 65 feet of water. GVSU scientist Bopaiah A. Biddanda said the sinkholes are home to "bizarre" ecosystems dominated by brilliant purple mats of cyanobacteria, or blue-green algae, but largely devoid of fish.

The sinkholes, some of which are larger than a football field, are similar to Karst sinkholes on land. Biddanda said this is the first time that scientists have documented such sinkholes in the Great Lakes; he said there are likely more sinkholes elsewhere in the lakes.

The discovery is further proof that the Great Lakes are far more complex than most of us realize.